Steam engine

ABSTRACT

A steam engine of a modified uniflow type having a valve and valve actuating mechanism permitting double-acting cylinders to operate efficiently under high speed-low torque conditions and also to be smoothly adjusted, during engine operation, for lower compression-higher torque operation at low start-up speeds. A chain driven, double cam, valve actuating mechanism permits smooth variations in the timing of valve operation with a simple control system so that even unskilled operators can run the engine, without roughness, through its full speed and torque ranges. A novel cylinder design obtains what is substantially uniflow operation without undesirable high compression.

O Unlted States Patent 1 [111 3,788,193

OConnor Jan. 29, 1974 STEAM ENGINE Primary Examiner-Paul E. Maslousky h3490 E. [76] Inventor g zgyfi gf gggga Calif Attorney, Agent, orFirm-Wolfe, Hubbard, Leydlg,

91 107 Voit & Osann, Ltd.

[22] Filed: Oct. 4, 1971 [57] ABSTRACT PP NO: 1867069 A steam engine ofa modified uniflow type having a v valve and valve actuating mechanismpermitting dou- [52] US. Cl. 91/243, 91/187 le-a ing ylinders to operateefficiently under high [51] Int. Cl; F011 21/02, F011 31/14 pe -1 w rqueconditions and also to be smoothly [58] Field of Search 91/243, 187, 188adjusted, during engine p on, or o er compression-higher torqueoperation at low start-up speeds. A [56] References Cit d chaindriven,double cam, valve actuating mechanism UNITED STATES PATENTS permitssmooth variations in the timing of valve opera- 1 076 256 10/1913 91/243tion with a simple control system so that even un- 1531053 M1925 's91/243 skilled operators can run the engine, without rough- 1 924 6898/1933 Knight I: :1: 91/187 6S5, through its full speed and W ranges- Anovel 2:688:955 9 1954 Ricardo .7 91/187 Cylinder design Obtains What isSubstantially uniflow FOREIGN PATENTS OR APPLICATIONS operation withoutundesirable high compression. 46,277 7 1939 Netherlands 91 187 4 Claims,9 Drawing Figures PATENTED JAN 2 91974 SHEET a [If 3 STEAM ENGINEDESCRIPTION OF THE INVENTION This invention relates generally tomechanical power generating steam engines and more particularly concernsa steam engine valving arrangement.

A characteristic of conventional piston type steam engines which hasrestricted their applications, particularly in recent years, is thatgood operating efficiency is normally achieved by designing the enginefor rather narrow ranges of speed and load. For example, a socalleduniflow type engine in which steam is admitted at the cylinder ends andexhausted at the cylinder center gives good efficiency at relativelyhigh speeds and low torques, because the cylinder ends remain hot, thereis high compression, and only short periods of outside emission.However, when such an engine is slowed down and more torque is demanded,efficiency is impaired.

Steam engines for handling wide variations in speed and load, in orderto retain reasonable overall efficiency, are therefore normally designedas multiple expansion engines or are otherwise burdened with structuralcomplications, which increase costs and, in themselves, reduceefficiencies.

Accordingly, it is the primary aim of this invention to provide a steamengine capable of operating very efficiently under high speed-low torqueconditions but which can be smoothly adjusted for low speed-high torqueoperation without roughness. As a result of the above operatingcharacteristic, the engine of the invention is well suited for use asthe propeller power plant for boats since cruising speed efficiency isobtained without sacrificing low speed maneuvering ability.

Another object of the invention is to provide an engine of the abovetype which is relatively uncomplicated and hence economical tomanufacture and maintain. i

A further object is to provide, in an engine as characterized above, asimple, easily understood control arrangement by which the engine can besafely and efficiently operated even by relatively inexperiencedpersonnel.

It is also an object to provide anengine of the above kind having theadvantages of uniflow operation without undesirably high compression.

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to thedrawings, in

which:

FIG. 1 is a fragmentary partially sectioned elevation of a steam engineembodying the invention;

FIG. 2 is a section taken approximately along the line 22 in FIG. 1;

FIG. 3 is a section taken approximately along the line 33 of FIG. 1;

FIG. 4 is a partially schematic perspective showing a portion of thestructure appearing in the previous figures;

FIG. 5 is an enlarged elevation of one of the cams developed in theengine of FIG. 1; and

FIGS. 6, 7, Band 9 are stop motion views similar to FIG. 1 showing theparts in different positions of operation. I

While the invention will be described in connection with a preferredembodiment, it will be understood that I do not intend to limit theinvention to that embodiment. On the contrary, I intend to cover allalternatives, modifications and equivalents as may be included withinthe spirit and scope of the invention.

Turning now to the drawings, there is shown a steam engine 10 embodyingthe invention but which is only partially illustrated for clarity andsimplicity of description. The engine 10 includes a main bed plate 11supporting a cylinder head 12 receiving a reciprocating piston 13coupled to a power output crank shaft 14 and which is operated by avalve 15 driven by a timing assembly 16. The assembly 16 is supported ona'frame plate 17, fixed to the bed plate 11, which also journals thecrank shaft 14 in bearings 18. The crank shaft is associated with a flywheel, not shown, and the primary power utilization device, such as aboat propeller.

Although only one cylinder head 12 and valve 15 is illustrated, it willbe apparent that additional heads and valves may be alined along thecrank shaft 14 to make the engine 10 multi-cylindered. As those skilledin the art will appreciate, the connections between the crank shaft andadditional cylinders would be angularly phased so as to smooth out theapplication of power to the crank shaft.

The piston 13 is coupled to the crank shaft 14 through a rod 21 pivotedon a crank 22 that is journalled on an eccentric section 23 of the crankshaft 14.

The cylinder head 12 includes a block 24 defining a cylinder 25 and avalve chamber 26 whose opposite ends are sealed by head and basecastings 27 and 28. The engine 10 is double-acting and hence bothcastings 27, 28 define, together with side plates 29, steam supplypassages 31 for conveying steam in the direction of the arrows 32 (seeFIG. 1) to the opposite ends of the valve chamber 26. I

Pursuant to one aspect of the invention, the cylinder 25 is of amodified uniflow type having steam admission ports 41 and 42 at eachend, a primary steam exhaustion port in the form of a number of smallopenings 43 at the cylinder middle, and a pair of auxiliary exhaustionports 44 and 45 at intermediate portions of the cylinder between theprimary exhaustion port openings 43 and the admission ports 41, 42.Cooperating with these ports is a spool-like valve element 46 slidablytitted in the valve chamber 26 and having a pair of land portions 47 and48 spaced for alternately opening the admission ports 41,- 42 whilekeeping the primary exhaustion port openings 43 open and simultaneouslyopening and closing the auxiliary port 44 or 45 farthest from the thenopen admission port.

The functioning sequence can be readily seen in FIGS. 6 through 9. InFIG. 6, the engine 10 is stopped and both admission ports 41, 42 areclosed. Movement of the valve element 46 upwardly, as to the-positionshown in FIG. 7, opens the admission port 42 so as to admit steam anddrive the piston 13 upwardly and the engine in a given direction.Movement of the valve element 46 downwardly from its FIG. 6 positionwould. have started the piston 13 in a downward direction and the enginein the reverse direction. With the valve element 46 in its FIG. 7position, the auxiliary port 44 is also open venting the upper half ofthe cylinder through the center portion of the element 46 and out to anexhaust passage 49 defined by an element 51 secured to the block 24.

After the valve element 46 remains in its FIG. 7 position for abrieftime period, the length of which deterhave been cleared by the piston.The return down- I stroke of the piston 13 is initiated by movement ofthe valve element 46 down to the FIG. 9 position in which the admissionport 41 is opened as well as the auxiliary exhaustion port 45. After atimed amount of steam is admitted to the upper end of the cylinder 25,the valve element 46 is again centered and the cycle repeated. Thosefamiliar with this art will recognize that the engine 10 has substantialsimilarity to the uniflow type of engine in that steam exhaustion takesplace at the middle of the cylinder thus keeping the ends of thecylinder hot and permitting relatively high compression buildups whichare, of course, factors that make a uniflow engine efficient during highspeed-low torque operation. It will be noted that movement of the valveelement 46 through its FIG. 6 to FIG. 8 positions during a short timeinterval will admit only a small amount of steam into the lower end ofthe cylinder-25 and will also quickly close off the auxiliary exhaustionport 44 so as to obtain a virtually classic uniflow operation.

On the other hand, for example when low speed-high torque operation iscalled for, the valve element 46 can be left in its FIG. 7 position fora longer time interval with the result that more steam is admitted forpowering the upward stroke of the piston 13 and the auxiliary exhaustport 44 is left open for a greater length of time to minimize thecompression against which the piston must act.

In accordance with the invention, the timing assembly 16 moves the valveelement 46 from its center blocking position to, alternatively, its twoadmission port opening positions for finite periods of time, measuredagainst crank shaft rotation, that may be varied while the engine isrunning. In the illustrated embodiment, the valve element 46 isconnected by a slide rod to a whiffle tree 56 at a pivot point 57. Theopposite ends of the whiffle tree 56 are pivoted to ears 58 on a pair ofbox cam followers 59 embracing, and riding on, the top and .bottomperipheries of a pair of identical earns 61 and 62 rotating with camshafts 63 and 64, re-

is coupled by apair of gears 65 (see FIG. 4) to a valve shaft 66 havingkeyed thereto a pair of sprockets 67 and 68. A chain 69 couples thesprocket 67 to a sprocket 71 keyed on the camshaft 64. A second chain 72couples the sprocket'68 to a sprocket 73 keyed on the other cam shaft63. The chains 69, 72 are trained over idler sprockets 74 running freelyon their respective supports, including an idler shaft 75 and a pair ofblocks 76 and 77. The illustrated arrangement also includes a thirdchain 78 and a pair of sprockets 79 for driving an auxiliary power shaft81.

In carrying out the invention, each cam 61, 62 (see FIG. 5) has high andlow peripheral portions defined by a segment 82 of a smaller basecircle, having a radius 84, and a segment 83 of a larger dwell circle,having a radius 85, disposed 180 apart, with the remainder of the camperiphery being arcs smoothly fairing into the circle segments 82, 83 sothat the cam has the same dimension between all parallel lines tangentto the pcriphery, such as the line pairs 86 and 87. Because of thisuniform peripheral cross dimension, the earns 61, 62 fit closely withinthe box followers 59 in all angular positions of their supporting camshafts 63, 64.

The earns 61, 62 as shown in FIG. 3, are 90 out of phase but it can beseen that when the cams are out of phase the valve element 67 will notbe moved from its center, port blocking position upon rotation of thecam shafts 63, 64 as, in that situation, the whiffle tree 56 will simplybe rocked by the box followers 59 moving up and down in exact butopposite sequence. However, by-varying the angular phase relationshipbetween the cams 61, 62 up to the point where the cams are in phase, theupper or ear portions of both box followers will, for a given intervalof cam rotation, ride on the dwell circle segments 83 of both cams andon the base circle segments 82 of both cams. When on the dwell circlesegments, the valve element 67 will have been lifted to its FIG. 7position, and when the ear portions of the box followers'59 ride on bothbase circle segments 82, the valve element 46 will have been shifteddown to its FIG. 9 position. At other times the valve element is inmovement or held in its port blocking, FIGS. 6 and 8 position.

In order to shift the angular phaserelationship of the cams 61, 62whether or not the engine is running, the chain 72 has substantialslackness and the block 76 supporting the idler sprockets 74 isshiftable so as to vary the effective length of chain in the oppositeruns connecting the sprockets 68 and 73. This obviously changes the camangular phase relationship. In the illustrated arrangement, a simple rod90 threaded through a lug 91 mounted on the plate 17 is provided forshifting the block 76. l

To get the engine started in the desired rotational direction, that isin forward or reverse, the chain 69 also has substantial slackness andan actuator 92, anchored to the lug 91, is provided to-shift the idlerblock 77 between two limit positions. This movement is sufficient torotate the cam shaft 64 180 with respect to the crank shaft 14 so as tothereby reverse engine rotation when steam is again supplied to theengine.

While the cams 61, 62 for the application illustrated have theircircular segments 82, 83 of substantially equal angular length so thateach admission port 41,42 is opened approximately the same length oftime for a given crank shaft speed, it will'be seen that using a cam ofthis shape toconvert rotary t'o reciprocating motion results inanarrangement wherein the extentof reciprocating motion that isdeveloped is the difference between the radii 84, 85, and the pause ordwell time created by the cam is dependent upon the relative angularlengths of the circular segments 82, 83. Theselengths obviously need notbe of similar angular extent, and hence the shape of the cams 61,62permits significant versatility of design.

It will be apparent from the foregoing that simple adjustment of thethreaded rod 90 can change, during engine operation, the engine valvecut-off" time so as to produce the flexibility of valve settingsdiscussed above in connection with FIGS. 6 through 9. For example,during engine startup under relatively high torque, the adjustment ofthe rod 90 would normally be such to leave the appropriate steamadmission port and corresponding auxiliary exhaustion port open for asubstantial number of degrees of crank shaft rotation. Once higherspeeds and lower torque. requirements are reached, the rod 90 may bereadjusted to achieve the uniflow typeof operation discussed abovethereby taking advantage of the efficiency inherent in such a design.

It will have been noted that the cams 66, 62 of the timing assembly 16not only permit variation in valve timing while the engine is running,but that this adjustment is infinitely variable'through a wide range.Stated in terms often used in the art, the assembly 16 controls theratio between the admission and the expansion portions of each cycle andcut-off, the event dividing admission and expansion, is infinitelyvariable. As a result, the engine can be readily adjusted for optimumefficiency.

Those familiar with this art will appreciate that the engine 10 is of astraightforward, relatively uncomplicated design and hence economical tomanufacture and maintain.

1 claim as my invention:

1. In a steam engine, the combination comprising, a cylinder headdefining a cylinder with a steam admission port at one end and a steamexhaustion port at an intermediate portion of the cylinder, a pistonfitted for reciprocation in said cylinder, a crank shaft coupled to saidpiston so that reciprocation of the piston rotates said shaft, saidcylinder head defining a valve chamber adjacent said cylinder with asteam inlet passage adjacent said admission port and a steam dischargepassage adjacent said exhaustion port, a valve element mounted in saidchamber for movement between a first position in-which said ports areblocked to a second position in which said ports are opened to therespective adjacent passages, a pair of identical cams each having highand low portions coupled to be driven by said crank shaft, a whiffletree connected to said valve element and riding on said cams so thatwhen the cams are 180 out of phase the valve element is not moved out ofsaid first position as the whiffle tree is rocked by the cams, and meansfor varying the angular phase relationship between said cams so that,for every full revolution of the cams, the whiffle tree rides for finiteperiods of time depending on said phase relationship on both of saidhigh portions and on both of said low portions whereby the whiffle treemoves the valve element to said second position for one of said periodsof time.

2. The combination of claim 1 in which said means is effective forsmoothly and continuously varying said phase relationship while saidcrank shaft is rotating so as to permit adjustmentof the time periodsaid valve element is in said second position from zero to a maximumvalue while the engine is running.

3. The combination of claim 2 in which said crank shaft drives ones ofsaid cams, and said means includes a chain coupling sprockets mountedfor rotation with both of said cams, said chain having substantialslackness, and said means also including a pair of mutually shiftableidler sprockets positioned for taking out said chain slackness, wherebymutually shifting said idler sprockets varies the angular phaserelationship between said cams.

4. The combination of claim 1 in which said cylinder has steam admissionports at each end and a pair of steam exhaustion ports at mid-portionsof the cylinder, said valve chamber having steam inlet passages adjacenteach of said admission ports and a steam discharge passage adjacent bothof said exhaustion ports, said valve element having a first position inwhich all of said ports are blocked, a second position in which oneadmission port is open' to the adjacent inlet passage and one exhaustionport is open to the adjacent discharge passage, and a third position inwhich the other admission port and exhaustion port are opened to theiradjacent passages, and said cams having their high and low portions ofequal angular length so that, when the cams are not 180 out of phase,the valve element is shifted tions.

1. In a steam engine, the combination comprising, a cylinder headdefining a cylinder with a steam admission port at one end and a steamexhaustion port at an intermediate portion of the cylinder, a pistonfitted for reciprocation in said cylinder, a crank shaft coupled to saidpiston so That reciprocation of the piston rotates said shaft, saidcylinder head defining a valve chamber adjacent said cylinder with asteam inlet passage adjacent said admission port and a steam dischargepassage adjacent said exhaustion port, a valve element mounted in saidchamber for movement between a first position in which said ports areblocked to a second position in which said ports are opened to therespective adjacent passages, a pair of identical cams each having highand low portions coupled to be driven by said crank shaft, a whiffletree connected to said valve element and riding on said cams so thatwhen the cams are 180* out of phase the valve element is not moved outof said first position as the whiffle tree is rocked by the cams, andmeans for varying the angular phase relationship between said cams sothat, for every full revolution of the cams, the whiffle tree rides forfinite periods of time depending on said phase relationship on both ofsaid high portions and on both of said low portions whereby the whiffletree moves the valve element to said second position for one of saidperiods of time.
 2. The combination of claim 1 in which said means iseffective for smoothly and continuously varying said phase relationshipwhile said crank shaft is rotating so as to permit adjustment of thetime period said valve element is in said second position from zero to amaximum value while the engine is running.
 3. The combination of claim 2in which said crank shaft drives ones of said cams, and said meansincludes a chain coupling sprockets mounted for rotation with both ofsaid cams, said chain having substantial slackness, and said means alsoincluding a pair of mutually shiftable idler sprockets positioned fortaking out said chain slackness, whereby mutually shifting said idlersprockets varies the angular phase relationship between said cams. 4.The combination of claim 1 in which said cylinder has steam admissionports at each end and a pair of steam exhaustion ports at mid-portionsof the cylinder, said valve chamber having steam inlet passages adjacenteach of said admission ports and a steam discharge passage adjacent bothof said exhaustion ports, said valve element having a first position inwhich all of said ports are blocked, a second position in which oneadmission port is open to the adjacent inlet passage and one exhaustionport is open to the adjacent discharge passage, and a third position inwhich the other admission port and exhaustion port are opened to theiradjacent passages, and said cams having their high and low portions ofequal angular length so that, when the cams are not 180* out of phase,the valve element is shifted for equal time periods into said second andthird positions.